Sickles typically including cutter bars supporting a row of knives, have been used to cut plants, including, but not limited to, hay, grasses, small grains and the like, for many years. The knives are composed of a plurality of knife or sickle sections which are mounted in side by side relation forming an elongate metal knife assembly. The elongate knife assembly is normally supported so as to slide longitudinally along an elongate stationary bar that has forwardly projecting, spaced apart guards bolted to a structural beam. The knife assembly moves back and forth in a reciprocating movement to move the knives relative to the guards so that the leading knife edges of the knives cross over the guards or through slots in the guards. This produces a shearing or cutting action which severs plant stems and stalks or other material captured between the knives and the guards.
In a harvesting machine, such as a combine or windrower, the knife assembly and stationary bar are typically supported in connection with a cutting head or header, and are oriented so as to extend sidewardly along a forward edge portion of structure such as a floor or pan of the header, hereinafter sometimes referred to generally as the floor. The floor or pan defines the lower periphery of a cut crop or plant flow area, which can include conveying apparatus, such as one or more augers or belts, operable in cooperation with a reel in machines so equipped, for conveying the cut plant material and crops, for instance, to a feeder inlet of a combine or windrow forming apparatus of a windrower.
The knife assembly is driven reciprocatingly longitudinally by an oscillating drive, which can include, but is not limited to, an eccentric shaft on a rotating hub, a wobble drive, or a similar well known commercially available device. Such drives are typically located at the sides of the header, so as to drive the knife assembly from the end. This location is advantageous as it allows the driving point for the knife assembly to be in line with the stationary bar, provides clearances for removal of the knife assembly, and provides space for assembly of the drive. Disadvantages of the side location include that the header must include significant frame structure for supporting the drive and to withstand forces and vibrations generated thereby. The end structure or crop divider at the end of the header must also be relatively wide, to accommodate the drive and to direct adjacent standing crops therepast, and increasing the possibility of accidentally pushing down adjacent standing crops. Additionally, for headers utilizing two drives located on opposite sides of the header, it is usually desired to time the operation of the drives such that the forces and vibrations generated by the respective drives cancel one another. This typically involves relatively long mechanical drive lines connecting the two drives together, which is disadvantageous as it adds weight, cost and complexity.
A knife assembly, which will weigh from 35 to 38 pounds for a typical 20 foot wide header, typically must accelerate and decelerate two times per cycle as a result of the reciprocating movement. A typical speed for the knife assembly is up to about 16 hertz or cycles per second. Thus, it can be seen, the reciprocating motion at a high cycle per second generates high acceleration values and high deceleration values that in turn generate high forces on the structural components. These high forces can have at least two negative effects, vibration at the drive system that may be transmitted to other components of the machine, and fatigue failure of the structural components themselves. On larger headers, for instance, headers 30feet wide and greater, two knife assemblies each equal to one-half the sideward extent of the header are often used.
Driving a knife assembly or assemblies of a header from a more central location, such as the center of the header, would provide several advantages compared to a side location. Notably among these advantages, the header structure would not be required to support heavy drive units on one or both sides, such that the structure of the header could be lighter. Long timing apparatus extending between the ends could also be eliminated. If the drive mechanism could be incorporated into a location that would not interrupt or require dividing crop or plant material flow through the crop flow area of the header, the normal crop flow of the header would not be significantly impacted. And, since the drives are not located in the ends, the end dividers can be made significantly thinner, such that the header can have a shorter overall width, would be more easily maneuverable in relation to adjacent standing crop, and danger of downing the adjacent standing crop would be reduced.
Thus, what is sought is a drive for a sickle of a header of an agricultural cutting machine, such as a combine or windrower, which overcomes one or more of the problems, negative effects, and disadvantages referenced above.